Draytek Vigor2710 Series User Manual page 52

Loop through
Backup Phone Number
the same SIP server, sometimes, the VoIP phone call
connection may not succeed. By using the specified dial out
account, the successful connection can be assured.
For the model of Vigor 2710Vn, the selection should be as the
following:
When the VoIP phone is obstructs or the Internet breaks down
for some reasons, the backup phone will be dialed out to
replace the VoIP phone number. At this time, the phone call
will be changed from VoIP phone into PSTN call according to
the loop through direction chosen. Note that, during the phone
switch, the blare of phone will appear for a short time. And
when the VoIP phone is switched into the PSTN phone, the
telecom co. might charge you for the connection fee. Please
type in backup phone number (PSTN number) for this VoIP
phone setting.
44 Vigor2710 Series User's Guide